Water change questions

[reefwithareefer]

I have a few questions about my top off and water change ratios that I hope someone can chime in on.

The reason I ask is that, even though my API tests says 0, I must have more if I have this brownish red algae/dust growing on the substrate and glass. It looks like the same stuff that J&L has in their bowfront display tank. I would like to find a way to make it go away and water changes seems to be the place to start. Or is it something that water changes will not make a difference to?

Sooooo.

Do I factor in my top off water when calculating how much of a water change I should do?

First, is there a product that can monitor how much top off water I use a day, week, month? Too absent minded and time constrained to visually monitor bucket volume per day to figure out

I have approx 360 gallons of water in the sump and tank. The Apex is set up to do daily water changes, about 4 gallons a day. Not sure if I need/should jump that up a bit yet, as my parameters are supposedly good by API and Salifert. (0 Phosphate, 0 nitrate, 0 ammonia, 420 ca, 1300 mag, 9.5 alk).

The daily saltwater changes work out to be around a 16% water change every 2 weeks.

If I use approx 5 gallons of ro/di top off/fresh water a day it would bring the water change ratio up to approx 25%, which seems to be a good ratio.

Do I include the top off water in my water change volume or not. Do i increase the water change to 25% every 2 weeks by adding another 35 gallons of saltwater instead of including the top off?

If it matters, I run about 2 cups of GFO and 3 cups of GAC in separate reactors, 50 mg of ozone thru a Bubble King 250 and that is all I run.

Feed frozen once a day (gone within 2 minutes, some land on substrate, but shrimp etc get them pretty quick) and very small amount of pellets (15) twice a day to 15 fish (avg 1.5 to 2 inches)

All softies,zoas, lps and sps doing very well.

Run 360w of Actinic t5 from 8 am til 7 pm and 750 watts of MH from 1:30 till 6:00 pm

Display is 290 gal has in/direct sunlight almost all day

Temp is an avg of 77, orp is 330 high and 280 low